#include "hashtable.h"
#include "snapshot.h"
-#include "snapshotimp.h"
#include "mymemory.h"
#include "common.h"
#define FAILURE(mesg) { model_print("failed in the API: %s with errno relative message: %s\n", mesg, strerror(errno)); exit(EXIT_FAILURE); }
-#ifdef CONFIG_SSDEBUG
-#define SSDEBUG model_print
-#else
-#define SSDEBUG(...) do { } while (0)
-#endif
-
-/* extern declaration definition */
-struct SnapShot *snapshotrecord = NULL;
-
/** PageAlignedAdressUpdate return a page aligned address for the
* address being added as a side effect the numBytes are also changed.
*/
return (void *)((((uintptr_t)addr) + PAGESIZE - 1) & ~(PAGESIZE - 1));
}
-#if !USE_MPROTECT_SNAPSHOT
-/** @statics
-* These variables are necessary because the stack is shared region and
-* there exists a race between all processes executing the same function.
-* To avoid the problem above, we require variables allocated in 'safe' regions.
-* The bug was actually observed with the forkID, these variables below are
-* used to indicate the various contexts to which to switch to.
-*
-* @savedSnapshotContext: contains the point to which takesnapshot() call should switch to.
-* @savedUserSnapshotContext: contains the point to which the process whose snapshotid is equal to the rollbackid should switch to
-* @snapshotid: it is a running counter for the various forked processes snapshotid. it is incremented and set in a persistently shared record
-*/
-static ucontext_t savedSnapshotContext;
-static ucontext_t savedUserSnapshotContext;
-static snapshot_id snapshotid = 0;
+#if USE_MPROTECT_SNAPSHOT
+
+/* Each SnapShotRecord lists the firstbackingpage that must be written to
+ * revert to that snapshot */
+struct SnapShotRecord {
+ unsigned int firstBackingPage;
+};
+
+/** @brief Backing store page */
+typedef unsigned char snapshot_page_t[PAGESIZE];
-#else /* USE_MPROTECT_SNAPSHOT */
+/* List the base address of the corresponding page in the backing store so we
+ * know where to copy it to */
+struct BackingPageRecord {
+ void *basePtrOfPage;
+};
+
+/* Struct for each memory region */
+struct MemoryRegion {
+ void *basePtr; // base of memory region
+ int sizeInPages; // size of memory region in pages
+};
/** ReturnPageAlignedAddress returns a page aligned address for the
* address being added as a side effect the numBytes are also changed.
return (void *)(((uintptr_t)addr) & ~(PAGESIZE - 1));
}
-/** The initSnapShotRecord method initialized the snapshotting data
- * structures for the mprotect based snapshot.
- */
-static void initSnapShotRecord(unsigned int numbackingpages, unsigned int numsnapshots, unsigned int nummemoryregions)
+/* Primary struct for snapshotting system */
+struct mprot_snapshotter {
+ mprot_snapshotter(unsigned int numbackingpages, unsigned int numsnapshots, unsigned int nummemoryregions);
+ ~mprot_snapshotter();
+
+ struct MemoryRegion *regionsToSnapShot; //This pointer references an array of memory regions to snapshot
+ snapshot_page_t *backingStore; //This pointer references an array of snapshotpage's that form the backing store
+ void *backingStoreBasePtr; //This pointer references an array of snapshotpage's that form the backing store
+ struct BackingPageRecord *backingRecords; //This pointer references an array of backingpagerecord's (same number of elements as backingstore
+ struct SnapShotRecord *snapShots; //This pointer references the snapshot array
+
+ unsigned int lastSnapShot; //Stores the next snapshot record we should use
+ unsigned int lastBackingPage; //Stores the next backingpage we should use
+ unsigned int lastRegion; //Stores the next memory region to be used
+
+ unsigned int maxRegions; //Stores the max number of memory regions we support
+ unsigned int maxBackingPages; //Stores the total number of backing pages
+ unsigned int maxSnapShots; //Stores the total number of snapshots we allow
+
+ MEMALLOC
+};
+
+static struct mprot_snapshotter *mprot_snap = NULL;
+
+mprot_snapshotter::mprot_snapshotter(unsigned int backing_pages, unsigned int snapshots, unsigned int regions) :
+ lastSnapShot(0),
+ lastBackingPage(0),
+ lastRegion(0),
+ maxRegions(regions),
+ maxBackingPages(backing_pages),
+ maxSnapShots(snapshots)
{
- snapshotrecord = (struct SnapShot *)model_malloc(sizeof(struct SnapShot));
- snapshotrecord->regionsToSnapShot = (struct MemoryRegion *)model_malloc(sizeof(struct MemoryRegion) * nummemoryregions);
- snapshotrecord->backingStoreBasePtr = (struct SnapShotPage *)model_malloc(sizeof(struct SnapShotPage) * (numbackingpages + 1));
+ regionsToSnapShot = (struct MemoryRegion *)model_malloc(sizeof(struct MemoryRegion) * regions);
+ backingStoreBasePtr = (void *)model_malloc(sizeof(snapshot_page_t) * (backing_pages + 1));
//Page align the backingstorepages
- snapshotrecord->backingStore = (struct SnapShotPage *)PageAlignAddressUpward(snapshotrecord->backingStoreBasePtr);
- snapshotrecord->backingRecords = (struct BackingPageRecord *)model_malloc(sizeof(struct BackingPageRecord) * numbackingpages);
- snapshotrecord->snapShots = (struct SnapShotRecord *)model_malloc(sizeof(struct SnapShotRecord) * numsnapshots);
- snapshotrecord->lastSnapShot = 0;
- snapshotrecord->lastBackingPage = 0;
- snapshotrecord->lastRegion = 0;
- snapshotrecord->maxRegions = nummemoryregions;
- snapshotrecord->maxBackingPages = numbackingpages;
- snapshotrecord->maxSnapShots = numsnapshots;
+ backingStore = (snapshot_page_t *)PageAlignAddressUpward(backingStoreBasePtr);
+ backingRecords = (struct BackingPageRecord *)model_malloc(sizeof(struct BackingPageRecord) * backing_pages);
+ snapShots = (struct SnapShotRecord *)model_malloc(sizeof(struct SnapShotRecord) * snapshots);
}
-/** HandlePF is the page fault handler for mprotect based snapshotting
+mprot_snapshotter::~mprot_snapshotter()
+{
+ model_free(regionsToSnapShot);
+ model_free(backingStoreBasePtr);
+ model_free(backingRecords);
+ model_free(snapShots);
+}
+
+/** mprot_handle_pf is the page fault handler for mprotect based snapshotting
* algorithm.
*/
-static void HandlePF(int sig, siginfo_t *si, void *unused)
+static void mprot_handle_pf(int sig, siginfo_t *si, void *unused)
{
if (si->si_code == SEGV_MAPERR) {
model_print("Real Fault at %p\n", si->si_addr);
}
void* addr = ReturnPageAlignedAddress(si->si_addr);
- unsigned int backingpage = snapshotrecord->lastBackingPage++; //Could run out of pages...
- if (backingpage == snapshotrecord->maxBackingPages) {
+ unsigned int backingpage = mprot_snap->lastBackingPage++; //Could run out of pages...
+ if (backingpage == mprot_snap->maxBackingPages) {
model_print("Out of backing pages at %p\n", si->si_addr);
exit(EXIT_FAILURE);
}
//copy page
- memcpy(&(snapshotrecord->backingStore[backingpage]), addr, sizeof(struct SnapShotPage));
+ memcpy(&(mprot_snap->backingStore[backingpage]), addr, sizeof(snapshot_page_t));
//remember where to copy page back to
- snapshotrecord->backingRecords[backingpage].basePtrOfPage = addr;
+ mprot_snap->backingRecords[backingpage].basePtrOfPage = addr;
//set protection to read/write
- if (mprotect(addr, sizeof(struct SnapShotPage), PROT_READ | PROT_WRITE)) {
+ if (mprotect(addr, sizeof(snapshot_page_t), PROT_READ | PROT_WRITE)) {
perror("mprotect");
// Handle error by quitting?
}
}
-#endif /* USE_MPROTECT_SNAPSHOT */
-
-#if !USE_MPROTECT_SNAPSHOT
-void createSharedMemory()
-{
- //step 1. create shared memory.
- void *memMapBase = mmap(0, SHARED_MEMORY_DEFAULT + STACK_SIZE_DEFAULT, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0);
- if (MAP_FAILED == memMapBase)
- FAILURE("mmap");
-
- //Setup snapshot record at top of free region
- snapshotrecord = (struct SnapShot *)memMapBase;
- snapshotrecord->mSharedMemoryBase = (void *)((uintptr_t)memMapBase + sizeof(struct SnapShot));
- snapshotrecord->mStackBase = (void *)((uintptr_t)memMapBase + SHARED_MEMORY_DEFAULT);
- snapshotrecord->mStackSize = STACK_SIZE_DEFAULT;
- snapshotrecord->mIDToRollback = -1;
- snapshotrecord->currSnapShotID = 0;
-}
-#endif
-
-/** The initSnapshotLibrary function initializes the snapshot library.
- * @param entryPoint the function that should run the program.
- */
-#if USE_MPROTECT_SNAPSHOT
-
-void initSnapshotLibrary(unsigned int numbackingpages,
+static void mprot_snapshot_init(unsigned int numbackingpages,
unsigned int numsnapshots, unsigned int nummemoryregions,
unsigned int numheappages, VoidFuncPtr entryPoint)
{
struct sigaction sa;
sa.sa_flags = SA_SIGINFO | SA_NODEFER | SA_RESTART | SA_ONSTACK;
sigemptyset(&sa.sa_mask);
- sa.sa_sigaction = HandlePF;
+ sa.sa_sigaction = mprot_handle_pf;
#ifdef MAC
if (sigaction(SIGBUS, &sa, NULL) == -1) {
model_print("SIGACTION CANNOT BE INSTALLED\n");
exit(EXIT_FAILURE);
}
- initSnapShotRecord(numbackingpages, numsnapshots, nummemoryregions);
+ mprot_snap = new mprot_snapshotter(numbackingpages, numsnapshots, nummemoryregions);
- // EVIL HACK: We need to make sure that calls into the HandlePF method don't cause dynamic links
+ // EVIL HACK: We need to make sure that calls into the mprot_handle_pf method don't cause dynamic links
// The problem is that we end up protecting state in the dynamic linker...
// Solution is to call our signal handler before we start protecting stuff...
siginfo_t si;
memset(&si, 0, sizeof(si));
si.si_addr = ss.ss_sp;
- HandlePF(SIGSEGV, &si, NULL);
- snapshotrecord->lastBackingPage--; //remove the fake page we copied
+ mprot_handle_pf(SIGSEGV, &si, NULL);
+ mprot_snap->lastBackingPage--; //remove the fake page we copied
void *basemySpace = model_malloc((numheappages + 1) * PAGESIZE);
void *pagealignedbase = PageAlignAddressUpward(basemySpace);
user_snapshot_space = create_mspace_with_base(pagealignedbase, numheappages * PAGESIZE, 1);
- addMemoryRegionToSnapShot(pagealignedbase, numheappages);
+ snapshot_add_memory_region(pagealignedbase, numheappages);
void *base_model_snapshot_space = model_malloc((numheappages + 1) * PAGESIZE);
pagealignedbase = PageAlignAddressUpward(base_model_snapshot_space);
model_snapshot_space = create_mspace_with_base(pagealignedbase, numheappages * PAGESIZE, 1);
- addMemoryRegionToSnapShot(pagealignedbase, numheappages);
+ snapshot_add_memory_region(pagealignedbase, numheappages);
entryPoint();
}
-#else
-void initSnapshotLibrary(unsigned int numbackingpages,
+
+static void mprot_add_to_snapshot(void *addr, unsigned int numPages)
+{
+ unsigned int memoryregion = mprot_snap->lastRegion++;
+ if (memoryregion == mprot_snap->maxRegions) {
+ model_print("Exceeded supported number of memory regions!\n");
+ exit(EXIT_FAILURE);
+ }
+
+ mprot_snap->regionsToSnapShot[memoryregion].basePtr = addr;
+ mprot_snap->regionsToSnapShot[memoryregion].sizeInPages = numPages;
+}
+
+static snapshot_id mprot_take_snapshot()
+{
+ for (unsigned int region = 0; region < mprot_snap->lastRegion; region++) {
+ if (mprotect(mprot_snap->regionsToSnapShot[region].basePtr, mprot_snap->regionsToSnapShot[region].sizeInPages * sizeof(snapshot_page_t), PROT_READ) == -1) {
+ perror("mprotect");
+ model_print("Failed to mprotect inside of takeSnapShot\n");
+ exit(EXIT_FAILURE);
+ }
+ }
+ unsigned int snapshot = mprot_snap->lastSnapShot++;
+ if (snapshot == mprot_snap->maxSnapShots) {
+ model_print("Out of snapshots\n");
+ exit(EXIT_FAILURE);
+ }
+ mprot_snap->snapShots[snapshot].firstBackingPage = mprot_snap->lastBackingPage;
+
+ return snapshot;
+}
+
+static void mprot_roll_back(snapshot_id theID)
+{
+#if USE_MPROTECT_SNAPSHOT == 2
+ if (mprot_snap->lastSnapShot == (theID + 1)) {
+ for (unsigned int page = mprot_snap->snapShots[theID].firstBackingPage; page < mprot_snap->lastBackingPage; page++) {
+ memcpy(mprot_snap->backingRecords[page].basePtrOfPage, &mprot_snap->backingStore[page], sizeof(snapshot_page_t));
+ }
+ return;
+ }
+#endif
+
+ HashTable< void *, bool, uintptr_t, 4, model_malloc, model_calloc, model_free> duplicateMap;
+ for (unsigned int region = 0; region < mprot_snap->lastRegion; region++) {
+ if (mprotect(mprot_snap->regionsToSnapShot[region].basePtr, mprot_snap->regionsToSnapShot[region].sizeInPages * sizeof(snapshot_page_t), PROT_READ | PROT_WRITE) == -1) {
+ perror("mprotect");
+ model_print("Failed to mprotect inside of takeSnapShot\n");
+ exit(EXIT_FAILURE);
+ }
+ }
+ for (unsigned int page = mprot_snap->snapShots[theID].firstBackingPage; page < mprot_snap->lastBackingPage; page++) {
+ if (!duplicateMap.contains(mprot_snap->backingRecords[page].basePtrOfPage)) {
+ duplicateMap.put(mprot_snap->backingRecords[page].basePtrOfPage, true);
+ memcpy(mprot_snap->backingRecords[page].basePtrOfPage, &mprot_snap->backingStore[page], sizeof(snapshot_page_t));
+ }
+ }
+ mprot_snap->lastSnapShot = theID;
+ mprot_snap->lastBackingPage = mprot_snap->snapShots[theID].firstBackingPage;
+ mprot_take_snapshot(); //Make sure current snapshot is still good...All later ones are cleared
+}
+
+#else /* !USE_MPROTECT_SNAPSHOT */
+
+#include <ucontext.h>
+
+#define SHARED_MEMORY_DEFAULT (100 * ((size_t)1 << 20)) // 100mb for the shared memory
+#define STACK_SIZE_DEFAULT (((size_t)1 << 20) * 20) // 20 mb out of the above 100 mb for my stack
+
+struct fork_snapshotter {
+ void *mSharedMemoryBase;
+ void *mStackBase;
+ size_t mStackSize;
+ volatile snapshot_id mIDToRollback;
+ ucontext_t mContextToRollback;
+ snapshot_id currSnapShotID;
+};
+
+static struct fork_snapshotter *fork_snap = NULL;
+
+/** @statics
+* These variables are necessary because the stack is shared region and
+* there exists a race between all processes executing the same function.
+* To avoid the problem above, we require variables allocated in 'safe' regions.
+* The bug was actually observed with the forkID, these variables below are
+* used to indicate the various contexts to which to switch to.
+*
+* @savedSnapshotContext: contains the point to which takesnapshot() call should switch to.
+* @savedUserSnapshotContext: contains the point to which the process whose snapshotid is equal to the rollbackid should switch to
+* @snapshotid: it is a running counter for the various forked processes snapshotid. it is incremented and set in a persistently shared record
+*/
+static ucontext_t savedSnapshotContext;
+static ucontext_t savedUserSnapshotContext;
+static snapshot_id snapshotid = 0;
+
+static void createSharedMemory()
+{
+ //step 1. create shared memory.
+ void *memMapBase = mmap(0, SHARED_MEMORY_DEFAULT + STACK_SIZE_DEFAULT, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0);
+ if (MAP_FAILED == memMapBase)
+ FAILURE("mmap");
+
+ //Setup snapshot record at top of free region
+ fork_snap = (struct fork_snapshotter *)memMapBase;
+ fork_snap->mSharedMemoryBase = (void *)((uintptr_t)memMapBase + sizeof(struct fork_snapshotter));
+ fork_snap->mStackBase = (void *)((uintptr_t)memMapBase + SHARED_MEMORY_DEFAULT);
+ fork_snap->mStackSize = STACK_SIZE_DEFAULT;
+ fork_snap->mIDToRollback = -1;
+ fork_snap->currSnapShotID = 0;
+}
+
+/**
+ * Create a new mspace pointer for the non-snapshotting (i.e., inter-process
+ * shared) memory region. Only for fork-based snapshotting.
+ *
+ * @return The shared memory mspace
+ */
+mspace create_shared_mspace()
+{
+ if (!fork_snap)
+ createSharedMemory();
+ return create_mspace_with_base((void *)(fork_snap->mSharedMemoryBase), SHARED_MEMORY_DEFAULT - sizeof(struct fork_snapshotter), 1);
+}
+
+static void fork_snapshot_init(unsigned int numbackingpages,
unsigned int numsnapshots, unsigned int nummemoryregions,
unsigned int numheappages, VoidFuncPtr entryPoint)
{
- if (!snapshotrecord)
+ if (!fork_snap)
createSharedMemory();
void *base_model_snapshot_space = malloc((numheappages + 1) * PAGESIZE);
//step 2 setup the stack context.
ucontext_t newContext;
getcontext(&newContext);
- newContext.uc_stack.ss_sp = snapshotrecord->mStackBase;
+ newContext.uc_stack.ss_sp = fork_snap->mStackBase;
newContext.uc_stack.ss_size = STACK_SIZE_DEFAULT;
makecontext(&newContext, entryPoint, 0);
/* switch to a new entryPoint context, on a new stack */
/* switch back here when takesnapshot is called */
pid_t forkedID = 0;
- snapshotid = snapshotrecord->currSnapShotID;
+ snapshotid = fork_snap->currSnapShotID;
/* This bool indicates that the current process's snapshotid is same
as the id to which the rollback needs to occur */
bool rollback = false;
while (true) {
- snapshotrecord->currSnapShotID = snapshotid + 1;
+ fork_snap->currSnapShotID = snapshotid + 1;
forkedID = fork();
if (0 == forkedID) {
/* If the rollback bool is set, switch to the context we need to
return to during a rollback. */
if (rollback) {
- setcontext(&(snapshotrecord->mContextToRollback));
+ setcontext(&(fork_snap->mContextToRollback));
} else {
/*Child process which is forked as a result of takesnapshot
call should switch back to the takesnapshot context*/
int status;
int retVal;
- SSDEBUG("The process id of child is %d and the process id of this process is %d and snapshot id is %d\n",
+ DEBUG("The process id of child is %d and the process id of this process is %d and snapshot id is %d\n",
forkedID, getpid(), snapshotid);
do {
retVal = waitpid(forkedID, &status, 0);
} while (-1 == retVal && errno == EINTR);
- if (snapshotrecord->mIDToRollback != snapshotid) {
+ if (fork_snap->mIDToRollback != snapshotid) {
exit(EXIT_SUCCESS);
}
rollback = true;
}
}
}
-#endif
-/** The addMemoryRegionToSnapShot function assumes that addr is page aligned.
- */
-void addMemoryRegionToSnapShot(void *addr, unsigned int numPages)
+static snapshot_id fork_take_snapshot()
{
-#if USE_MPROTECT_SNAPSHOT
- unsigned int memoryregion = snapshotrecord->lastRegion++;
- if (memoryregion == snapshotrecord->maxRegions) {
- model_print("Exceeded supported number of memory regions!\n");
- exit(EXIT_FAILURE);
- }
-
- snapshotrecord->regionsToSnapShot[memoryregion].basePtr = addr;
- snapshotrecord->regionsToSnapShot[memoryregion].sizeInPages = numPages;
-#endif //NOT REQUIRED IN THE CASE OF FORK BASED SNAPSHOTS.
-}
-
-/** The takeSnapshot function takes a snapshot.
- * @return The snapshot identifier.
- */
-snapshot_id takeSnapshot()
-{
-#if USE_MPROTECT_SNAPSHOT
- for (unsigned int region = 0; region < snapshotrecord->lastRegion; region++) {
- if (mprotect(snapshotrecord->regionsToSnapShot[region].basePtr, snapshotrecord->regionsToSnapShot[region].sizeInPages * sizeof(struct SnapShotPage), PROT_READ) == -1) {
- perror("mprotect");
- model_print("Failed to mprotect inside of takeSnapShot\n");
- exit(EXIT_FAILURE);
- }
- }
- unsigned int snapshot = snapshotrecord->lastSnapShot++;
- if (snapshot == snapshotrecord->maxSnapShots) {
- model_print("Out of snapshots\n");
- exit(EXIT_FAILURE);
- }
- snapshotrecord->snapShots[snapshot].firstBackingPage = snapshotrecord->lastBackingPage;
-
- return snapshot;
-#else
swapcontext(&savedUserSnapshotContext, &savedSnapshotContext);
- SSDEBUG("TAKESNAPSHOT RETURN\n");
+ DEBUG("TAKESNAPSHOT RETURN\n");
return snapshotid;
-#endif
}
-/** The rollBack function rollback to the given snapshot identifier.
- * @param theID is the snapshot identifier to rollback to.
- */
-void rollBack(snapshot_id theID)
+static void fork_roll_back(snapshot_id theID)
{
-#if USE_MPROTECT_SNAPSHOT == 2
- if (snapshotrecord->lastSnapShot == (theID + 1)) {
- for (unsigned int page = snapshotrecord->snapShots[theID].firstBackingPage; page < snapshotrecord->lastBackingPage; page++) {
- memcpy(snapshotrecord->backingRecords[page].basePtrOfPage, &snapshotrecord->backingStore[page], sizeof(struct SnapShotPage));
- }
- return;
- }
-#endif
-
-#if USE_MPROTECT_SNAPSHOT
- HashTable< void *, bool, uintptr_t, 4, model_malloc, model_calloc, model_free> duplicateMap;
- for (unsigned int region = 0; region < snapshotrecord->lastRegion; region++) {
- if (mprotect(snapshotrecord->regionsToSnapShot[region].basePtr, snapshotrecord->regionsToSnapShot[region].sizeInPages * sizeof(struct SnapShotPage), PROT_READ | PROT_WRITE) == -1) {
- perror("mprotect");
- model_print("Failed to mprotect inside of takeSnapShot\n");
- exit(EXIT_FAILURE);
- }
- }
- for (unsigned int page = snapshotrecord->snapShots[theID].firstBackingPage; page < snapshotrecord->lastBackingPage; page++) {
- if (!duplicateMap.contains(snapshotrecord->backingRecords[page].basePtrOfPage)) {
- duplicateMap.put(snapshotrecord->backingRecords[page].basePtrOfPage, true);
- memcpy(snapshotrecord->backingRecords[page].basePtrOfPage, &snapshotrecord->backingStore[page], sizeof(struct SnapShotPage));
- }
- }
- snapshotrecord->lastSnapShot = theID;
- snapshotrecord->lastBackingPage = snapshotrecord->snapShots[theID].firstBackingPage;
- takeSnapshot(); //Make sure current snapshot is still good...All later ones are cleared
-#else
- snapshotrecord->mIDToRollback = theID;
+ fork_snap->mIDToRollback = theID;
volatile int sTemp = 0;
- getcontext(&snapshotrecord->mContextToRollback);
+ getcontext(&fork_snap->mContextToRollback);
/*
* This is used to quit the process on rollback, so that the process
* which needs to rollback can quit allowing the process whose
*/
if (!sTemp) {
sTemp = 1;
- SSDEBUG("Invoked rollback\n");
+ DEBUG("Invoked rollback\n");
exit(EXIT_SUCCESS);
}
/*
* This fix obviates the need for a finalize call. hence less dependences for model-checker....
*/
- snapshotrecord->mIDToRollback = -1;
+ fork_snap->mIDToRollback = -1;
+}
+
+#endif /* !USE_MPROTECT_SNAPSHOT */
+
+/**
+ * @brief Initializes the snapshot system
+ * @param entryPoint the function that should run the program.
+ */
+void snapshot_system_init(unsigned int numbackingpages,
+ unsigned int numsnapshots, unsigned int nummemoryregions,
+ unsigned int numheappages, VoidFuncPtr entryPoint)
+{
+#if USE_MPROTECT_SNAPSHOT
+ mprot_snapshot_init(numbackingpages, numsnapshots, nummemoryregions, numheappages, entryPoint);
+#else
+ fork_snapshot_init(numbackingpages, numsnapshots, nummemoryregions, numheappages, entryPoint);
+#endif
+}
+
+/** Assumes that addr is page aligned. */
+void snapshot_add_memory_region(void *addr, unsigned int numPages)
+{
+#if USE_MPROTECT_SNAPSHOT
+ mprot_add_to_snapshot(addr, numPages);
+#else
+ /* not needed for fork-based snapshotting */
+#endif
+}
+
+/** Takes a snapshot of memory.
+ * @return The snapshot identifier.
+ */
+snapshot_id take_snapshot()
+{
+#if USE_MPROTECT_SNAPSHOT
+ return mprot_take_snapshot();
+#else
+ return fork_take_snapshot();
+#endif
+}
+
+/** Rolls the memory state back to the given snapshot identifier.
+ * @param theID is the snapshot identifier to rollback to.
+ */
+void snapshot_roll_back(snapshot_id theID)
+{
+#if USE_MPROTECT_SNAPSHOT
+ mprot_roll_back(theID);
+#else
+ fork_roll_back(theID);
#endif
}